1. Field of the Invention
The present invention relates to a signal transmitting device and a signal transmitting method suitable for application to a case of transmitting an image signal output from an image sensor of a double density Bayer structure, for example.
2. Description of the Related Art
In the past, development of receiving systems and image pickup systems for ultrahigh resolution video signals surpassing an HD (High Definition) signal as a current image signal (video signal) in which one frame is 1920 samples×1080 lines is underway. For example, UHDTV (Ultra High Definition TV) standards as a next-generation broadcasting system having 4 times or 16 times the number of pixels of current HD are being established by international societies. The international societies include the ITU (International Telecommunication Union) and SMPTE (Society of Motion Picture and Television Engineers).
Video standards proposed to the ITU and SMPTE relate to video signals of 3840 samples×2160 lines or 7680 samples×4320 lines, which video signals have twice or four times the number of samples and the number of lines of a video signal of 1920 samples×1080 lines. Of the video standards, the standard established by the ITU is referred to as LSDI (Large Screen Digital Imagery), and is referred to as UHDTV proposed to SMPTE.
There are two kinds of sample structure of pixels as follows in the 4096 standards defined by SMPTE 2048-1 and SMPTE 2036-1 (UHDTV), as shown in FIGS. 14A and 14B.
FIGS. 14A and 14B are diagrams of assistance in explaining an example of sample structure of the 4096 standards. One frame used for description in FIGS. 14A and 14B is formed by 4096 samples×2160 lines (hereinafter referred to also as one frame of a 4 k×2 k signal). There are three kinds of sample structure of the 4096 standards as follows. Incidentally, in the SMPTE standards, signals to which a dash (′) is attached, such as R′, G′, B′ and the like, represent signals resulting from gamma correction or the like.
FIG. 14A shows an example of an R′G′B′ or Y′Cb′Cr′ 4:4:4 system. In this system, all samples include RGB or YCbCr components.
FIG. 14B shows an example of a Y′Cb′Cr′ 4:2:2 system. In this system, even samples include YCbCr components, and odd samples include Y components.
Differences between a normal Bayer structure and a double density Bayer structure will be described in the following with reference to FIGS. 15A and 15B.
In the past, an image pickup device using an image pickup element of a Bayer structure is commonly known. Such an image pickup element captures the image light of a subject through a color filter, and outputs an image signal according to the intensity of the image light. Then, a subsequent processing section subjects the image signal to predetermined processing. The image pickup device can thereby display an image on a viewfinder or an external display device. In the image pickup element, R, G, and B pixels capable of outputting R, G, and B signals, respectively, are generally arranged in a predetermined pattern. Resolution differs depending on how the R, G, and B pixels are arranged.
FIG. 15A shows an example of the normal Bayer structure.
In the normal Bayer structure, two G pixels are arranged on a diagonal line, and an R pixel and a B pixel are arranged on a diagonal line orthogonal to the diagonal line of the G pixels. However, the normal Bayer structure provides only half the number of pixels of a 4 k×2 k signal on a G ch, which has a largest number of pixels.
FIG. 15B shows an example of the double density Bayer structure.
In the double density Bayer structure, pixels in the normal Bayer structure shown in FIG. 15A are arranged obliquely at 45°. The pixels have half the size of the pixels in the normal Bayer structure in a vertical direction and a horizontal direction. Thus, a double density Bayer G ch has a resolution corresponding to the number of pixels of a 4 k×2 k signal. The size of one pixel becomes correspondingly small, but does not need to be made smaller than in a case of providing 4 k×2 k pixels on the G ch in the normal Bayer structure, because of the oblique arrangement. Thus, resolution and sensitivity are made compatible with each other in a well-balanced manner, which is an advantage over the normal Bayer structure.
In addition, Japanese Patent Laid-Open No. 2005-328494 discloses a technique for transmitting a 3840×2160/30 P, 30/1.001 P/4:4:4/12-bit signal, which is a kind of 4 k×2 k signal (ultrahigh resolution signal of 4 k samples and 2 k lines), at a bit rate of 10 Gbps or more. Incidentally, [3840×2160/30 P] denotes [number of pixels in the horizontal direction]×[number of lines in the vertical direction]/[number of frames per second]. In addition, [4:4:4] denotes a ratio of [red signal R:green signal G:blue signal B] in a case of a primary-color signal transmission system and a ratio of [luminance signal Y:first color-difference signal Cb:second color-difference signal Cr] in a case of a color-difference signal transmission system.